[jimmuller]

Just curious. Mine read low when cold, of course, then increase as I drive. When I start after the car has been sitting for a while the four wheels often don't read the same,with a difference of 1 or 2 psi. As the tires warm, sometimes a sensor will jump up by 2, such as from 33 to 35. Sometimes they converge to, say, 36, but may not stay identical.

Now it may be that +/- 1 psi, or even +/- 2 is all the precision one can expect. I wouldn't know. I've never had a car before that could display the pressures.

 

[antennahead]

Mine always say "32" all the way around when cold, once warmed up they increase, hot daytime temps and more agressive driving will run them higher as well. Usually the rears end up 1 or 2 pounds higher than the fronts. Not unusual to see 35 fronts and 36 rears once warmed up. They are consistant though, if you monitor then regularly when driving, that's how I knew I had something wrong with my right rear tire. Left rear was at 36 and the right rear wouldn't budge from 32. I look at this every day I drive, first when cold and then once warmed up. When I got home and inspected the tire closely, there was the nail I posted about in the other thread.

 

[InTgr8r]

Just curious. Mine read low when cold, of course, then increase as I drive. When I start after the car has been sitting for a while the four wheels often don't read the same,with a difference of 1 or 2 psi. As the tires warm, sometimes a sensor will jump up by 2, such as from 33 to 35. Sometimes they converge to, say, 36, but may not stay identical.

Now it may be that +/- 1 psi, or even +/- 2 is all the precision one can expect. I wouldn't know. I've never had a car before that could display the pressures.

Mine are the same [edit]as yours.[/edit]
The sensors are definitely not hi-res output

 

[jimmuller]

Mine are the same.
The sensors are definitely not hi-res output

The same. Same as what? Each other or same as mine?

 

[InTgr8r]

The same. Same as what? Each other or same as mine?

lol... sorry about the unintended double entendre.
Mine are the same as yours.

 

[jimmuller]

lol... sorry about the unintended double entendre.
Mine are the same as yours.

So you didn't intend the double entendre?
The nice thing about ambiguity is it can be taken so many different ways.

(Thanks.)

 

[DriveInHouston]

If it is cool when I start, it is 32 all around. As the tires warm up, they get to 33 all around, and then to 35 unevenly, with no discernible pattern. Sometimes the front ones first, sometimes the rear ones first and occasionally, in a diagonal pattern.

I have never, ever, seen 34 psi, nor 36.

I don’t worry about 1 psi difference between tires, all I care is not having one lose pressure precipitously (a flat).

 

[duegatti]

I think that the sensors are set to resolve different pressures at the 0.1 bar level. Since that equals 1.47 lb, we English unit people do not get resolution at 1 psi. And that is why certain psi values never appear, and are skipped over.

 

[jimmuller]

I think that the sensors are set to resolve different pressures at the 0.1 bar level. Since that equals 1.47 lb, we English unit people do not get resolution at 1 psi. And that is why certain psi values never appear, and are skipped over.

Sounds reasonable. Thanks. A followup question, senator. How much is significant? I wouldn't think 1 psi makes any real difference. 3 or 4 however, that's a matter of concern.

 

[duegatti]

Well, keep in mind, for the 20" wheels at least, they have a regular recommended pressure of 33 psi, and a "comfort" recommended pressure of 30 psi. So we can infer that 3 lb is not a concern. I think warning messages will appear around 25 psi - I think that would be a problem.

 

[GregW]

The heat of the sun on a tyre makes a difference in my pressures. When I fill the tyres at cold and never in the sun that morning, the pressures differ by less than .1 bar at any time and always even out during a longer drive.

The servo where I do the fill has a pump that adjusts by .05 bar.

 

[JazzCatGab]

My 18" P-Zeros start out at 29 psi, just like the manual says they should. On my country road jaunts, the rear tires go up to 30 psi before the fronts, but they soon follow. I think they typically end up the day at about 31-32 psi. On the track, they get up to 34-35 psi (if I recall right), which is nice because I don't get the sidewall scouring.

 

[jimmuller]

IIRC, the manual calls for 33psi at 68degF. Presumably that is the temperature when the car has been sitting. When I set them for 33 at 68F, they aren't at 33 on warmer days. So it's a moving target, so to speak.

 

[MLJJ]

19" P Zeros in Comfort and got a tire low light recently. The warned front left tire was 27 and the front right at 28 (no light). Rears were 29. I know, I've been negligent and will do better!

 

[JazzCatGab]

IIRC, the manual calls for 33psi at 68degF. Presumably that is the temperature when the car has been sitting. When I set them for 33 at 68F, they aren't at 33 on warmer days. So it's a moving target, so to speak.

Yep, you must have the 20" wheels, and the manual does say 33 for them.

 

[jimmuller]

Yep, you must have the 20" wheels, and the manual does say 33 for them.

Bingo! Of course it is rarely 68F when I start up the car in the morning. So, like said, it's a moving target.

 

[Dacar]

Just curious. Mine read low when cold, of course, then increase as I drive. When I start after the car has been sitting for a while the four wheels often don't read the same,with a difference of 1 or 2 psi. As the tires warm, sometimes a sensor will jump up by 2, such as from 33 to 35. Sometimes they converge to, say, 36, but may not stay identical.

Now it may be that +/- 1 psi, or even +/- 2 is all the precision one can expect. I wouldn't know. I've never had a car before that could display the pressures.

My least favorite option on car, truck , or RV. My reading do the same thing and change from tire to tire

 

[JazzCatGab]

My least favorite option on car, truck , or RV. My reading do the same thing and change from tire to tire

Interesting. On my 18" wheels, the pressures may vary between front and back, but usually just for a while. The backs always warm up quicker than the fronts, but the temps are pretty consistent at front or back even if they change.

 

[Naptown]

Pressure will vary if one side of the car is facing the sun for a significant amount of time.

 

[wriggly]

Just use a high quality air gauge, do it the old fashioned way and ignore the tpms.

They invented the [email protected] things because some dumb blonde killed herself in a Ford Explorer rollover from underinflated tires.